Auto-sensitized oxidation of Ru(II) complexes I. Studies on the stability of two Ru(II) complexes ([Ru(NH3)5NCPyR]3+, RCH3 and C6H5CH2) in a medium containing singlet oxygen
✍ Scribed by Antonio Eduardo da Hora Machado; Zenis N. Rocha; Elia Tfouni
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 593 KB
- Volume
- 88
- Category
- Article
- ISSN
- 1010-6030
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✦ Synopsis
The generation of singlet oxygen by a photochemical pathway, involving the excited state of a pentaammine Ru(II) complex ,:ontaining an N-substituted 4-cyanopyridine ligand and molecular oxygen in aqueous solution, is reported in this work. A :wo-step degradation process occurs by virtue of the action of singlet oxygen. This species promotes the oxidation of Ru(II) Io Ru(III) in the ground state of the complex. The cyanopyridine ligand then suffers hydrolysis, resulting in an Ru(III) complex ,:ontaining a carboxyamidopyridine ligand. The influence of the substituent on the stability of the complex in the presence ,~f singlet oxygen is studied, showing that a methyl substituent leads to a more stable complex than a benzyl substituent. A i:inetic treatment of this process shows that the quenching of singlet oxygen by the complex has diffusional character, and is ?redominantly physical. Chemical quenching is related to the electron transfer process between Ru(II) and singlet oxygen. :